Diseases affecting the cornea are a major cause of blindness worldwide, second only to cataract in overall importance. According to the World Health Organization, approximately 2 million new cases are reported each year. Over 50 million people in the world are blind in one or both eyes from corneal injury or disease. Degradation of visual acuity impacts many more.
For various reasons, current solutions for corneal blindness and diseases only address 5%-10% of cases. To date, most patients are treated with Keratoplasty—a procedure that relies on transplanting corneal tissue harvested, from the deceased. All artificial cornea solutions that are based on implants have failed to address this potential for diversified reasons. Due to risks, complexity, and costs, these are selectively used as a last resort for patients that are not suited for corneal transplant or have failed one. Current solutions for corneal blindness are divided to Keratoplasty (Corneal transplantation) and Keratoprosthesis (Artificial cornea).
During keratoplasty surgery the graft is taken from a recently deceased donor with no known diseases or other factors that may affect the chance of survival of the donated tissue or the health of the recipient. The disadvantage of keratoplasty is a lack of donor tissue, the complexity and costs of operating a cornea bank, and the limited applicability to only some cases. For example, corneal diseases and injuries that leads to vascularization (penetration of blood vessels into the corneal tissue) are not suitable for keratoplasty. Multiple grafting also leads to elevated risk for rejection/failure.
When using an artificial cornea the procedure is known as keratoprosthesis. Traditionally, keratoprosthesis is recommended after a patient has had a failure of one or more donor corneal transplants. While different types of Keratoprosthesis have been approved for limited use by the FDA (see Salvador-Culla et al. Journal of Functional Biomaterial. 2016, 7, 13, with a review of recent advances in the field of keratoprosthesis), the only viable solution in the marketplace today is the Boston KPro. Boston KPro is approved by the FDA only for cases that cannot be addressed by Keratoplasty. This is due to many complications and the need for close and lifelong monitoring by an ophthalmologist familiar with the Boston KPro. Life-long topical steroids such as prednisolone acetate is necessary in all KPro eyes to prevent inflammation.
There are multiple disadvantages and failures associated with the known keratoprosthesis options, including diversified, postoperative complications which are mainly a result of the device intervention in the physiology of the anterior chamber, Most of the patients (60%-75%) develop glaucoma, elevated intraocular pressure, which can lead to blindness, limited field of vision and cataract. Furthermore, there is poor biointegration of the known keratoprosthesis that necessitates daily antibiotic drops, lifelong treatment with topical steroids, and intensive lifelong ophthalmologist follow up.
After the implantation of known keratoprosthesis the access to the internal parts of the eye for performing surgical procedures such as cataract and retinal surgery is very limited at best. Due to this, the primary keratoprosthesis surgery is often combined with other procedures including implantation of glaucoma filtration devices, and a cataract surgery (replacing the lens with synthetic Intra Ocular Lens) making the procedure longer, more dangerous and costly.